1. Field of the Invention
The present invention generally relates to clockspring assemblies. More specifically, the invention relates to an electronic centering indicator for a clockspring assembly.
2. Description of Related Art
Substantially all automotive vehicles are now manufactured with one or more airbags. Typically, a driver's side airbag is provided in the steering wheel facing the driver of the vehicle, and a second airbag is provided in the portion of the instrument panel facing the front passenger seat of the vehicle. The present discussion concerns the airbag located in the steering wheel.
Because the various collision sensors of an automotive vehicle provide a signal causing inflation of the airbag instantaneously with initiation of a collision event, and sometimes prior to the collision event, the airbag must be in continuous electrical connection with the collision sensors and other electronics in the vehicle body. Thus, a driver side airbag requires that an electrical connection be continuously provided between the airbag, as it rotates with the steering wheel, and the stationary sensors and other electronics.
Electrical connections between rotatable and stationary parts are known. In one well known connection, an electric brush rests upon a conductive ring, with one of the parts being rotatable. However, with this type of connection there is a risk, during the early or pre-stages of a collision, that the brush may separate or lose contact with the conductive ring. This loss of contact may create a transient failure in the electrical connection, resulting in delayed deployment of the airbag.
Another type of connection between rotatable and stationary parts is a clockspring assembly or connector. Clockspring assemblies typically include an outer housing, a rotor member and a “clockspring.” The clockspring is a coil of flat cable having one end connected to a plug or terminal on the outer housing and the other end connected to a plug or terminal on the rotor. The terminal on the outer housing, also referred to as the hub, is further connected to the electronics in the car body and the terminal on the rotor is connected to other electronics on the steering wheel associated with the airbag. As the steering wheel rotates, the clockspring of the clockspring assembly is wound and unwound, depending on the direction of rotation, and provides a continuous wired connection between the two parts.
Clockspring assemblies are typically manufactured at the site of a specialty manufacturer and then shipped to the vehicle manufacturer where they are further installed with the steering wheel. Because of this, it is important that the position of the outer hub with respect to the rotor member remain in a known position so that the clockspring assembly can be installed in a centered position on the steering wheel. Such a position is one where the clockspring is capable of an equal amount of rotation in either direction, without the clockspring becoming completely wrapped or unwrapped around the rotor.
In view of the above, it is apparent that there is a need for a mechanism that ensures that the clockspring assembly is properly centered once installed on the column of the steering wheel, before the vehicle leaves the assembly plant, removing the possibility of over rotation of the clockspring assembly due to misassembly.